Solid state-vacuum wideband amplifier

ABSTRACT

A solid state-vacuum wideband amplifier is provided. The amplifier includes an electron source adapted to emit electrons in response to an rf signal and wideband rf signal input means connected to the electron source. The amplifier further includes means for accelerating the electrons toward an electron beam semiconductor current amplifying device and means for focusing and accelerating the electrons so that they will bombard the amplifying device. Wideband rf signal output means are connected to the amplifying device.

United States Patent Zinn Oct. 14, 1975 SOLID STATE-VACUUM WIDEBANDAMPLIFIER Inventor: Mortimer H. Zinn, Elberon, NJ.

Assignee: The United States of America as represented by the Secretaryof the Army, Washington, DC.

Filed: Sept. 30, 1974 Appl. No.: 510,516

US. Cl. 330/33; 330/44; 330/56 Int. Cl. H03F 3/60 Field of Search330/12, 33, 34, 44, 53,

References Cited UNITED STATES PATENTS lO/l97l Smith 315/94 OTHERPUBLICATIONS Taylor, Electron Beam-Semiconductor Amplifier,

1970 Conference on Electron Device Techniques, pp. 54-57.

Primary Examiner.lames B. Mullins Attorney, Agent, or Firm-NathanEdelberg; Robert P. Gibson; Arthur L. Bowers ABSIRACT 3 Claims, 4Drawing Figures /0 A? OUTPUT LM E55 l .D/ODE Tl. 4a

Rf S/GNAL Hy SOURCE \4 42/ l I I I SOLID STATE-VACUUM WIDEBAND AMPLIFIERThe invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment of anyroyalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates to widebandamplifiers and more particularly to a solid state-vacuum widebandamplifier.

Heretofore, amplifiers capable of operating within a range fromsubstantially dc to 800 or more megahertz utilized a hot cathode and atraveling wave deflection system. Such devices have several drawbacksstemming from their construction. These drawbacks include the largephysical size necessitated by the traveling wave deflection system;environmental problems resulting from the hot cathode and the expensesinvolved in their manufacture and production.

In view of the above, it is the principal object of the presentinvention to provide a solid state-vacuum wideband amplifier.

SUMMARY OF THE INVENTION The above and other beneficial objects andadvantages are attained in accordance with the present invention byproviding a solid state-vacuum amplifier which includes an electronsource adapted to emit electrons in response to an rf signal andwideband rf signal input means connected to the electron source. Theamplifier further includes means for accelerating the electrons towardan electron beam semiconductor current amplifying device and means forfocusing and accelerating the electrons so that they will bombard theamplifying device. Wideband rf signal output means are connected to theamplifying device.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 is the schematic representation of the wideband amplifier of thepresent invention;

FIG. 2 is an enlarged perspective view of a first embodiment of coldcathode and strip-line connector for use in the wideband amplifier ofFIG. 1;

FIG. 3 is a perspective and longitudinal sectional view of a secondembodiment of a cold cathode and strip-line connector for use in thewideband amplifier of FIG. 1, taken in part along reference lines 33 offragmentary FIG. 4 in the direction indicated by the arrows; forpurposes of clarity, section lines have been omitted from FIG. 3; and,

FIG. 4 is an enlarged perspective fragmentary view of the cathode end ofFIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present inventionis illustrated in the accompanying drawing wherein similar componentsbear the same reference numeral throughout the several views. Referenceis first made to FIG. 1 wherein the wideband amplifier of the presentinvention includes a novel solid statevacuum component having a coldcathode 12 coupled by capacitor 14 to an rf signal source 16. Inresponse to rf signal to component 10, cathode l2 emits electrons whichare accelerated toward an electron beam semiconductor (EBS) diode 18through a focusing electrode 20. The electrons emitted by cathode 12 areaccelerated toward diode 18 by a high voltage (on the order of lO-l5kv)low current power supply 22. A variable power supply 24 drives thefocusing electrodes to direct electrons emitted by the cold cathode tothe metallic connection 26 on the p layer of the electron beamsemiconductor diode 18. The diode 18 is connected to a low voltage highcurrent power supply 28 through a load resistor 30 across which theamplified rf output signal appears.

FIG. 2, 3 and 4 show details of two different embodiments of coldcathode 12, coupling copacitor and the connector 32 between the coldcathode 12 and rf signal source 16.

In the first embodiment shown in FIG. 2, the connector 32 is astrip-line 34 comprising an elongated base member 36 of dielectricmaterial carrying a pair of parallel coextensize conductor strips 38 and40. The stripline 34 overlies an electron emitting source comprising anelongated member 42 formed of dielectric material. The top surface ofmember 42 had applied to it in the active area designated by the bracket45, an SnO layer 44. A first conductive comb 46 and a second conductivecomb 48 overlies the dielectric material and the SnO layer. The combs 46and 48 have parallel side-byside extensions 50 and 52 underlying endportions of conductor strips 38 and 40 respectively near the end 54 ofstrip line 34. Conductive comb 46 has teeth 56 that interdigitate withsimilar teeth 58 of comb 48 in the active area 45. Electrons are emittedbetween the interdigitated teeth in response to an rf signal applied toconductive combs 46 and 48. When an rf signal is applied to conductorstrips 38 and 40 of strip-line 34 the signal is capacitively coupled toconductive combs 46 and 48 through the dielectric base member 36. Thesize of the metal teeth and their number per unit length of theconductive combs are designed for the emission density required for aparticular application.

In the second embodiment of the present invention depicted in FIGS. 3and 4, the electron source comprises an optoelectronic cold cathode 60(such devices have been developed by and are available from the RadioCorporation of America) in strip-line configuration having a top strip62 of heavily doped GaAs to serve as an ohmic contact. The top strip 62is bifurcated with prongs 64 and 66 extending longitudinally. A CsOcovered emission region 68 occupies the space between prongs 64 and 66and extends over a break 70 in a confining layer 72 that overlayssubstrate 74. The components of the cathode are as shown in FIG. 4.Suffice it to say that due to the configuration of the confining layer,photon emission is limited to the break in the confining layer so thatelectron emission is limited to the area between prongs 64 and 66 whenan rf signal is applied between contact 62 and a conductive layer 76underlying the substrate 74.

Referring to FIG. 3, it can be seen that the optoelectronic cold cathodeelectron emitter 60 forms an extension of strip-line 78 with strip 62forming an extension of conductive strip 80 and the conductive layer 76forming an extension of the conductive ground plane 82.

Strip-line 78, in turn, extends from strip-line which is capacitivelycoupled to an input strip-line 86 having a top ground plane 88, a firstdielectric layer 90, a conductive strip 92, second dielectric layer 94,and bottom ground plane 96. Dielectric layer 94, in fact, is

formed of two layers 98 and 100 with an extension 102 of conductivestrip 80 extending partially along the in terface between layers 98 and100 as shown.

The forward end 106 of strip-line 86 is stepped downwardly with the topsurface 108 of the stepped portion forming a continuation of the topground plane 88 of strip-line 86.

Strip-line 110 extends from the forward end of the stepped down portion106. This strip-line has a top ground plane 112, first dielectric layer114, conductive strip 1 16 which forms an intermediate integral segmentof conductive strip 80-102, second dielectric layer 118 which forms anextension of dielectric member 84, and a bottom ground plane 120 whichforms an extension of ground plane 82.

The input rf signal is applied between ground planes 88 and 96 andconductive layer 92. This signal is capacitively coupled (through thedielectric material) to strip extension 102 to appear on the prongs64,66 or between the prongs 64,66 and the ground plane 76. As before, anaccelerating voltage 22 is applied to strip 62 (through a connector suchas 122) to cause the emitted electrons to bombard the EBS diode.

In the above description, focusing electrodes 20 are disclosed to directthe emitted electrons to the EBS diode. It should be realized, however,that proximity focusing may be employed in place of the focusingelectrode by providing suitable dielectric spacers to maintain the coldcathode and diode in the proper physical relationship for directelectron bombardment.

Thus, in accordance with the above, the above stated object iseffectively attained.

Having thus described the invention, what is claimed 1. A solidstate-vacuum wideband amplifier comprismg,

a wideband rf signal input means,

a strip-line for connection to an rf signal source,

an rf responsive cold cathode electron source, a stripline connected tosaid electron source,

said strip-lines being capacitively coupled whereby said cathode emitselectrons in response to rf from said source,

an electron beam semiconductor current amplifying device responsive toincident bombarding electrons to generate an amplified current directlyresponsive to the bombarding electrons,

means for accelerating electrons emitted by said source toward saidelectron beam semiconductor current amplifying device,

means for focusing emitted electrons to bombard said semiconductorcurrent amplifying device, and wideband rf signal output means connectedto said current amplifying device.

2. The amplifier in accordance with claim 1 wherein said cold cathodeelectron source comprises an elongated member of dielectric material, anSnO layer overlying a surface of said elongated member; a firstconductive comb overlying said layer, and a second conductive comboverlying said layer, the teeth of said combs being interdigitated withspace between adjacent teeth of the two combs.

3. The amplifier in accordance with claim 1 wherein said electron sourcecomprises an optoelectronic cold cathode in strip-line configurationhaving a top strip with a portion consisting of heavily doped GaAs toserve as an ohmic contact, said top strip portion includes a bifurcatedportion having spaced apart prongs and said optoelectronic cold cathodefurther includes means for confining photons generated thereby toportions aligned with the spacing between said prongs whereby electronsare emitted between said prongs.

1. A solid state-vacuum wideband amplifier comprising, a wideband rfsignal input means, a strip-line for connection to an rf signal source,an rf responsive cold cathode electron source, a stripline connected tosaid electron source, said strip-lines being capacitively coupledwhereby said cathode emits electrons in response to rf from said source,an electron beam semiconductor current amplifying device responsive toincident bombarding electrons to generate an amplified current directlyresponsive to the bombarding electrons, means for accelerating electronsemitted by said source toward said electron beam semiconductor currentamplifying device, means for focusing emitted electrons to bombard saidsemiconductor current amplifying device, and wideband rf signal outputmeans connected to said current amplifying device.
 2. The amplifier inaccordance with claim 1 wherein said cold cathode electron sourcecomprises an elongated member of dielectric material, an SnO2layeroverlying a surface of said elongated member; a first conductive comboverlying said layer, and a second conductive comb overlying said layer,the teeth of said combs being interdigitated with space between adjacentteeth of the two combs.
 3. The amplifier in accordance with claim 1wherein said electron source comprises an optoelectronic cold cathode instrip-line configuration having a top strip with a portion consisting ofheavily doped GaAs to serve as an ohmic contact, said top strip portionincludes a bifurcated portion having spaced apart prongs and saidoptoelectronic cold cathode further includes means for confining photonsgenerated thereby to portions aligned with the spacing between saidprongs whereby electrons are emitted between said prongs.